Carriage shift mechanism for an electric typewriter

ABSTRACT

A cam loosely mounted on a constantly rotating drive shaft is normally held stationary independently of the drive shaft rotation and is permitted to rotate through a prescribed angle upon depression of the shift key or shift lock key of the typewriter. This rotary motion of cam is translated into the upward displacement of the typewriter carriage via a linkage coupled to a rail slidably supporting the carriage thereon. The linkage is further operatively coupled to a toggle joint mechanism adapted to assist the up-and-down motion of the carriage.

United States Patent 1191 Kubota et al. Oct. 7, 1975 CARRIAGE SHIFTMECHANISM FOR AN 1,805,685 5/1931 Conard 197/81 x ELECTRIC TYPEWRITER2,275,759 3/1942 Helmond 197/80 X 2,730,224 l/1956 Yaeger 197/74Inventors: Toshlhlro Kubota; Toshikatu 3,034,629 5/1962 Link 197/74Terashima, both of Sakakimachi, 3,157,265 11/1964 Palmer 1 197/72 XJapan 3,228,511 l/l966 Meinherz 197/74 3,273,684 9/1966 Oshiba etal197/72 x [73] Ass1gnee: Nakajlma All Kabushlkl Kaisha,

Tokyo Japan Primary Examiner-Clifford D. Crowder [22] Fil d; M 30, 1974Attorney, Agent, or Firm-Waters, Schwartz & Nissen [21] Appl. No.:474,689 [57] ABSTRACT A cam loosely mounted on a constantly rotatingdrive Foreign Appllcatlon y Data shaft is normally held stationaryindependently of the Nov. 19, 1973 Japan 48-129977 drive shaft rotationand is permitted to rotate through 1 a prescribed angle upon depressionof the shift key or [52] US. Cl 197/73; 197/80 shift lock key of thetypewriter. This rotary motion of [51] Int. CL B41J 11/14; B41J 25/08;B41J 25/24 cam is translated into the upward displacement of the [58]Field of Search 197/71, 72, 73, 74, 75, typewriter carriage via alinkage coupled to a rail slid- 197/76, 77, 78, 79, 80, 81 ablysupporting the carriage thereon. The linkage is further operativelycoupled to a toggle joint mecha- [56] References Cited nism adapted toassist the up-and-down motion of the UNITED STATES PATENTS carriage-743,259 11/1903 Donning 197/75 5 Claims, 6 Drawing Figures US. PatentOct.7,1975 Sheat 1 on 3,910,398

my v FIG.

US. Patent Oct. 7,1975 Sheet2 0f3 3,910,398

US. Patent Oct. 7,1975 Sheet 3 of3 3,910,398

CARRIAGE SHIFT MECHANISM FOR AN ELECTRIC TYPEWRITER BACKGROUND OF THEINVENTION This invention relates generally to typewriters and inparticular to electric typewriters. More specifically, the invention isdirected to a mechanism for shifting the carriage, and therefore theplaten, of an electric typewriter for the purpose of selective printingof capitals and small letters and of other characters or symbols on theupper and lower halves of the respective keys.

It is well known that in the electric typewriters of this class, anelectric motor drive is utilized to power the typing stroke, thecarriage reciprocation, and the carriage shifting. Since each of thesefunctions is performed by clutching the proper linkage to a drive shaftheld in constant rotation by the motor, it is necessary, for longertypewriter life and less operator fatigue, to minimize the load imposedon the drive shaft and the resistance offered by the keys. Much efforthas indeed been expended industrially to this end. However, in view ofthe current state of the art, at least the carriage shift mechanismseems to be still in need of further refinement to be of true practicalutility as it involves the greatest application of mechanical force.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide a novel and improved carriage shift mechanism for an electrictypewriter whereby the carriage can be shifted positively with minimumapplication of finger pressure to a key, and with no undue load imposedupon the constantly rotating drive shaft of the typewriter.

Another object of the invention is to provide a carriage shift mechanismof extremely simplified and inexpensive construction which can be easilyincorporated in electric typewriters of known configuration.

With these objects in view and the other objects here inafter set forth,this invention provides, in a typewriter of the class having aconstantly rotating drive shaft, a carriage shift mechanism whichincludes a cam loosely mounted on the drive shaft and normally heldstationary independently of the rotation of the drive shaft. Whenactuated by the shift key means of the typewriter, however, the camrotates with the drive shaft through a prescribed angle therebyactuating cam follower means at one end of linkage means adapted toimpart up-and-down motion to the carriage. The linkage means isconnected at the other end to a toggle joint mechanism, the operation ofwhich is initiated by the linkage means, to help the same impartup-anddown motion to the carriage. Hence the shifting of the carriagecan be accomplished if there is sufficient mechanical force produced tocause the two levers of the toggle joint to turn past theirstraight-line position.

The features which are believed to be novel and characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its configuration and mode ofoperation, together with the further objects and advantages thereof,will be best understood from the following description taken inconjunction with the accompanying drawing which illustrates, by way ofexample only, a preferred embodiment of the invention and in which likereference characters denote like parts in the several views.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a partly broken away perspective view of a carriage shiftmechanism constructed in accordance with the principles of thisinvention;

FIG. 2 is a side elevational view showing the essential parts of themechanism shown in FIG. 1;

FIG. 3 is an exploded perspective view showing the manner in which a camis mounted on the drive shaft of the typewriter in the arrangement ofFIG. 1;

FIG. 4 is a side elevational view showing how the cam is held stationaryin its normal position on the drive shaft;

FIG. 5 is a similar view showing how the cam is caused to rotate withthe drive shaft through a prescribed angle to its operative positionupon depression of the shift key or shift lock key of the typewriter;and

FIG. 6 is an exploded perspective view showing the manner in which thedrive shaft is coupled to a source of rotary power such as an electricmotor in the arrangement of FIG. 1.

DETAILED DESCRIPTION With particular to FIG. 1, reference numeral 1designates a drive shaft which is in constant rotation to power thesequentialimpression of characters from a group of type arranged onseparate rods (not shown) or other means in accordance with the priorart. The constant rotation of the drive shaft 1 is further utilizedaccording to this invention to effect a shift in the position of acarriage 2 and hence in the printing position of the typefaces againstthe paper for selection between capitals and small letters or betweenother characters or symbols on the upper and lower halves of therespective keys (not shown) of the typewriter.

For such shifting of the position of the carriage 2, the drive shaft 1has a cam 7 loosely mounted on one end thereof to impart the desiredup-and-down motion to the carriage 2 via linkage means comprising a pairof levers 3 and 4, a bell crank 5 and a link 6. Although not shown inthe drawing, it is assumed that the drive shaft 1 is coupled to a sourceof rotary power such as an electric motor via a pulley 8 and an endlessbelt 9, the pulley 8 being coupled to the drive shaft 1 via meansadapted to absorb any undue resistance offered to its rotation, as willhereinafter be set forth in more detail in connection with FIG. 6.

As seen more clearly in FIG. 2, the aforesaid pair of levers 3 and 4 arein scissorlike arrangement, both being turnably supported by a shaft 10at their crossing point. These levers 3 and 4 carry cam followers in theform of rollers 11 and 12 on their respective ends 30 and 4a disposedopposite the cam 7, and the other ends 3b and 4b of the respectivelevers 4,5 are yieldably urged against each other as by means of ahelical tension spring 13. These contacting ends 3b and 4b are partlyrecessed correspondingly to define a slot 15 therebetween. Slidablyreceived in this slot 15 is a pin 14 fixed to one end of the bell crank5 which is turnably supported, at the apex of the angle formed by itstwo arms, by a shaft 18 fixed in an elongate stationary member 17secured to the frame 16 (FIG. 1), of the typewriter. The other end ofthe bell crank 5 is turnably coupled to one end of the link 6 by a pinor shaft 19.

A carriage rail 21 is secured to the link 6 at or adjacent the other endthereof and the rail 21 is adapted to impart up-and-down motion directlyto the carriage 2 supporting a platen or cylinder in the usual manner.The link 6 further carries an adjustablestop 22 intermediate both endsthereof, the stop 22 being adapted to make contact with a bend portion23 of the stationary member 17 to determine the lower limit of theswinging motion of the link 6. Another adjustable stop 24 is supportedby the stationary member 17 to determine the upper limit of the swingingmotion of the link 6.

The said other end of the link 6 secured to the carriage rail 21 isfurther coupled by a pin or shaft 25 to one end of a lever 27 which isturnably supported by a shaft 26 at a point intermediate the two endsthereof. The other end of lever 27 is coupled by a pin or shaft to oneend of a lever 29 having a helical compression spring 28 wound somewhatloosely thereon. A toggle joint mechanism is thus formed by the levers27 and 29.

It will be seen from FIGS. 1 and 2 that the helical compression spring28 is supported between an annular member 29a loosely fitted over thelower end portion of the lever 29 and an abutment 29b formed at itsupper end. The lever-29 is further slotted longitudinally at its lowerend portion, as indicated at 29c, and a pin 32 on the frame 16 isslidably received in slot 29c in contact with the annular member 29athereby holding the same on the lever 29 against the force of the spring28. A helical tension spring 33 is stretched between the said other endof the link 6 and the frame 16, for purposes hereinafter made apparent.

As illustrated in detail in FIG. 3, the cam 7 loosely mounted on one endof the drive shaft 1 has a radial projection 7a and a slit 7b, thelatter being adapted to engage one end 34a of a helical spring 34 fittedover the drive shaft 1. The other end 341) of the spring 34 extendsradially outwardly with respect to the drive shaft 1 and, as seen inFIGS. 4 and 5, is thus adapted to engage either of the prongs 35a and35b of a fork 35. It is important to note that the spring 34 is of suchinside diameter that it is capable of simultaneous rotation with thedrive shaft 1, and further that the spring 34 is coiled in a directionopposite the direction of rotation of the drive shaft 1 indicated by thearrow a in FIG. 3.

Referring again to FIG. I, the fork 35 is supported by a shaft 36 fixedto the frame 16 so as to be swingable back and forth, or in directionsnormal to the drive shaft 1, and is further yieldably urged as by meansof a helical spring 37 in such a way that its prong 35a will normallyengage the end 34b of the spring 34. The fork 35 is coupled via a link38' to one end of a shift lever 39 which is swingable on a shaft 40 andwhich carries a Shift key 41 on the other, or forward, end thereof. Ashift lock key 42 is provided adjacent the shift key 41 in accordancewith the prior art. The shift lever 39 is provided with automatic returnmeans in the form of a helical tension spring 43.

As best shown in FIG. 6, the aforesaid pulley 8 has an axial bore 44therethrough adapted to receive a smaller diameter portion 1a of thedrive shaaft 1 with appropriate clearance. A lever 45 is mounted on theoutside of the pulley 8 by receiving a screw threaded portion lb of thedrive shaft 1 in its rectangular aperture, and another lever 48 ismounted further on the outside of the lever 45 by loosely receiving thescrew threaded portion 1b and by additionally receiving a stop pin 46projecting laterally from the pulley 8 in its rectangular aperture 47. Alock nut 49 is fitted over the screw threaded portion 1b to preventdetachment of the above listed parts from the drive shaft 1. A helical.

tension spring 50 is stretched between the levers 45 and 48, and a stoplug 45a is formed intergrally with the lever 45 to engage the otherlever 48 in such a way that the two levers 45 and 48 are normally heldin their respective positions illustrated in FIG. 1. A collar 51 is alsofitted over the drive shaft 1 on the inside of the pulley 8.

Proceeding to the description of operation of this preferred embodimentof the invention, it will be noted that FIG. 1 represents the normal orinoperative condition of the carriage shift mechanism, with the prong35a of the fork 35 in engagement with the end 34b of the spring 34 asillustrated in FIG. 4. Since the spring 34 is wound around the driveshaft 1 in the opposite direction to that of its rotation as previouslymentioned, the spring 34 is held stationary regardless of the rotationof the drive shaft 1 taking place in a direction tending to increase itsdiameter. The cam 7 is also held stationary on the rotating drive shaft1, so that the spring 34 is now held unloaded.

It is assumed that while the spring 34 is thus held unloaded, the cam 7engaging the end 34a of the spring in its slit 7b has its radialprojection directed up wardly as seen in FIG. 4. Thus, when the shiftkey 41 or shift lock key 42 is not depressed, the cam 7 is effective inraising the end 3a of the lever 3 via'the roller 11, contrary to thecondition represented in FIG. 2. The lever 3 thus caused to turnclockwise as. seen in FIG. 2 causes corresponding turning of the otherlever 4 via the spring 13, with the result that the bell crank 5 iscaused to turn counterclockwise via the pin 14 slidably received in theslot 15 between the ends 3b and 4b of the two levers 3 and 4. The link 6is then generally lowered to the position indicated in chain dottedlines in FIG. 2 thereby causing the lever 27 to turn counterclockwise.The lower portion of this lever 27 and the other lever, 29 thus movepast the straight-line position to their normal positions indicated bythe chain dotted lines in FIG. 2. The spring 28 is of course compressedby this motion of the lever 29.

Discussed in the preceding two paragraphs is the normal condition of thecarriage shift mechanismaccording to the invention, in which thecarriage rail 21 and therefore the carriage 2 carrying the platen 2thereon are held in lowered position, and in which the link 6 andassociated structure are held in their respective inoperative positionsin a stabilized manner. by the action of the compression spring 28 andthe balancing tension spring 33. The typist may now print the smallletters and other characters on the lower halves of the respective keys.

Upon depression of the shift key 41 or of the shift lock key 42, asindicated by way of an example in FIG. 5 by a finger 52 on the shift key41, the shift lever 39 turns counterclockwise on the shaft 40 to causeclockwise turning of the fork 35 via the link 38. The prong 35a of thefork 35 is now out of engagement with the end 34b of the spring 34, sothat the spring 34 together with its radially extending end 34b becomesfree to rotate simultaneously with the drive shaft 1. Since the otherprong 35b of the fork 35 has been displaced toward the drive shaft 1upon depression of the key 41 or 42, the end 34b of the spring 34 isthereby arrested shaft.

With its end 34b thus arrested by the prong 35b of the fork 35, thespring 34 is now held stationary on the drive shaft 1 rotating asaforesaid in the opposite direction to that in which the spring 34 iswound. Since the cam 7 engaging the end 34a of the spring 34 alsorotates in step therewith, its radial projection 70 becor'nes effectiveto lower the end 4a of the lever 4 via the roll 12 thereby causing thelevers 3 and 4 to turn counterclockwise to the respective positionsindicated in solid lines in FIG. 2. The bell crank 5 and the link 6 arefurther caused to assume their respective positions indicated in solidlines in FIG. 2.

This upward displacement of the link 6 is assisted by the toggle jointmechanism comprising the levers 27 and 29 as they move past theirstraight-line position by compressing the spring 28. The carriage 2 andtherefore the platen are thus shifted to their elevated position via thecarriage rail 21 to permit the typist to print the capitals and othercharacters on the upper halves of the respective keys. It will beunderstood that the carriage 2 and asociated linkages can be securelyretained in their elevated position by the toggle joint mechanism now inthe position indicated in solid lines in FIG. 2 as long as the shift key41 or shift lock key 42 is held depressed.

What is claimed is:

1. In a typewriter of the class having a source of rotary power, a driveshaft coupled to the source of rotary power to be thereby driven inconstant rotation, and a carriage capable of being selectively movedbetween raised and lowered positions, a carriage shift mechanismcomprising, in combination:

shift key means;

a cam mounted on the drive shaft to be rotatable relative to the driveshaft and normally held stationary independently of the rotation of saiddrive shaft;

means actuated by said shift key means to permit said cam to undergorotation through a prescribed angle together with said drive shaft;

cam follower means actuated by said cam upon its rotation through saidprescribed angle;

linkage means actuated by said cam follower means to impart up-and-downmotion to said carriage, said linkage means comprising a pair of leversin scissor-like crossed arrangement pivotably connected at central partsthereof and having respective first ends located on opposite sides ofsaid cam to form said cam follower means, said levers having oppositesecond ends resiliently urged into contact with each other, said secondends being partly recessed to define a slot therebetween, and link meanshaving an end with a pin thereon slidably received in said slot, saidlink means being connected at its other end to said carriage; and

toggle joint means coupled to said other end of said link means toassist the up-and-down motion of said carriage, said toggle joint meansbeing effective to selectively hold said link means and hence saidcarriage securely in said raised or lowered positions.

2. A carriage shift mechanism as claimed in claim 1, wherein said camfollower means comprises a pair of rollers respectively rotatablymounted on said first ends of said levers.

3. A carriage shift mechanism as claimed in claim 1, wherein said togglejoint means comprises:

a first lever pivotally supported at a pointintermediate the endsthereof, said first lever having one end pivotally coupled to said otherend of said link means;

a second lever having one end pivotally coupled to the other of saidends of said first lever, said second lever having a slot.formedlongitudinally therein;

a stationary pin slidably received in said slot of said second lever;and

a helical compression spring coiled around said second lever andsupported at one end by said stationary pin and at the other end by anabutment formed at said one end of said second lever.

4. A carriage shift mechanism as claimed in claim 1, wherein said meansactuated by said shift key means comprises:

a fork pivotably supported about an axis above said drive shaft, saidfork being connected to said shift key means and having a pair of prongsdisposed on opposite sides of said drive shaft; and

a spring coiled around said drive shaft so as to be capable ofsimultaneously rotation therewith, said spring having one end coupled tosaid cam and another end extending radially outwardly with respect tothe drive shaft to normally engage one of said prongs in such mannerthat said spring is normally prevented-from simultaneous rotation withsaid drive shaft.

5. A carriage shift mechanism as claimed in claim 1 wherein said linkmeans comprises a bellcrank having one arm on which said pin is fixed,and a link pivotably connected to said bellcrank at the other armthereof,

said line being connected to said carriage.

1. In a typewriter of the class having a source of rotary power, a driveshaft coupled to the source of rotary power to be thereby driven inconstant rotation, and a carriage capable of being selectively movedbetween raised and lowered positions, a carriage shift mechanismcomprising, in combination: shift key means; a cam mounted on the driveshaft to be rotatable relative to the drive shaft and normally heldstationary independently of the rotation of said drive shaft; meansactuated by said shift key means to permit said cam to undergo rotationthrough a prescribed angle together with said drive shaft; cam followermeans actuated by said cam upon its rotation through said prescribedangle; linkage means actuated by said cam follower means to impartupand-down motion to said carriage, said linkage means comprising a pairof levers in scissor-like crossed arrangement pivotably connected atcentral parts thereof and having respective first ends located onopposite sides of said cam to form said cam follower means, said levershaving opposite second ends resiliently urged into contact with eachother, said second ends being partly recessed to define a slottherebetween, and link means having an end with a pin thereon slidablyreceived in said slot, said link means being connected at its other endto said carriage; and toggle joint means coupled to said other end ofsaid link means to assist the up-and-down motion of said carriage, saidtoggle joint means being effective to selectively hold said link meansand hence said carriage securely in said raised or lowered positions. 2.A carriage shift mechanism as claimed in claim 1, wherein said camfollower means comprises a pair of rollers respectively rotatablymounted on said first ends of said levers.
 3. A carriage shift mechanismas claimed in claim 1, wherein said toggle joint means comprises: afirst lever pivotally supported at a point intermediate the endsthereof, said first lever having one end pivotally coupled to said otherend of said link means; a second lever having one end pivotally coupledto the other of said ends of said first lever, said second lever havinga slot formed longitudinally therein; a stationary pin slidably receivedin said slot of said second lever; and a helical compression springcoiled around said second lever and supported at one end by saidstationary pin and at the other end by an abutment formed at said oneend of said second lever.
 4. A carriage shift mechanism as claimed inclaim 1, wherein said means actuated by said shift key means comprises:a fork pivotably supported about an axis above said drive shaft, saidfork being connected to said shift key means and having a pair of prongsdisposed on opposite sides of said drive shaft; and a spring coiledaround said drive shaft so as to be capable of simultaneously rotationtherewith, said spring having one end coupled to said cam and anotherend extending radially outwardly with respect to the drive shaft tonormally engage one of said prongs in such manner that said spring isnormally prevented from simultaneous rotation with said drive shaft. 5.A carriage shift mechanism as claimed in claim 1 wherein said link meanscomprises a bellcrank having one arm on which said pin is fixed, and alink pivotably connected to said bellCrank at the other arm thereof,said line being connected to said carriage.